Showing papers on "Blade pitch published in 1968"

Improvements in or relating to blading arrangement for turbomachines

Abstract: 1,235,006. Turbines; axial flow compressors; jet propulsion plant. SOC NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION. Dec. 5, 1968 [Dec. 12, 1967], No. 57836/68. Headings F1C, F1J and F1T. A two-tier blade ring for a turbomachine such as a compressor ducted fan or the like comprises angularly spaced blades each formed by an inner section 2 having a tip portion 5 and a radially aligned outer section 3 having a base portion 6a mounted in a groove 6 in the tip 5. The blade sections 2, 3 are exposed to different working fluid flows, such as two air-flows or flows of air and combustion gases, and are separated by an annular member 1 having circumferentially spaced apertures engaging the tips 5 to strengthen the assembly. Insertion of each base 6a in its groove 6 is facilitated by a groove 7 in the member 1 in alignment with each aperture. As shown, the blades may be variable pitch having a spigot 4 secured in taper-roller bearings 8 in an annular member 9 fixed to the shaft r of a gas turbine engine compressor. Each spigot 4 carries Fig. 1, a gear 10 meshing with a rack 11 on an arm 12 secured to an axially slidable sleeve 13 mounted on shaft r. A hydraulic jack or other pneumatic, mechanical or electrical device can actuate the sleeve 13 to vary the blade pitch. In a modification, Fig. 6, the pitch varying mechanism comprises a toothed sector 21 secured to each spigot 4 and meshing with a gear 22 mounted on shaft r. Normally gear 22 rotates at the same speed as shaft r but can be rotated relative thereto to effect variation of the blade pitch. Fig. 5 (not shown) illustrates an arrangement in which two succesive two-tier compressor rotor stages have pitch varying mechanism as shown in Fig. 1, the respective control sleeves 13 being slidable in mutually opposite directions by a common hydraulic actuator (16) fixed to stator structure between the rotor stages. The two-tier stator blade rings (15) of the compressor may also be constructed similar to Fig. 1 with fixed or variable pitch blades.

Propeller lifting-surface corrections

Abstract: : Correction factors for camber, ideal angle due to loading, and ideal angle due to thickness, which are based on propeller lifting surface theory, are presented for a series of propellers. This series consists of optimum free- running propellers with chordwise loadings the same as an NACA a = 0.8 mean line and with NACA-66 chordwise thickness distributions. The results of the calculations show that the three-dimensional camber and ideal angle are generally greater than the two-dimensional camber and ideal angle at the same lift coefficient. The correction factors increase with increasing expanded area ratio, and those for camber and ideal angle due to loading decrease with increasing number of blades. Thickness, in general, induces a positive angle to the flow, which necessitates a correction to the blade pitch. This ideal angle is largest near the blade root and decreases to negligible values toward the blade tip and increases with increasing number of blades. Skew induces an inflow angle, necessitating a pitch change which is positive toward the blade root and negative toward the blade tip.

Rotary wing system

Abstract: A ROTARY WING SYSTEM FOR AIRCRAFT WHICH COMPRISES A RATATABLY MOUNTED HUB, AND A PLURALITY OF BLADES EACH CONNECTED TO THE HUB FOR ROTATION THEREWITH BY A RESPECTIVE BALL JOINT TO PERMIT MOVEMENT ABOUT THREE COORDINATE AXES INCLUDING THE LONGITUDINAL AXIS OF THE BLADE. BLADE PITCH CONTROL MEANS ROTATABLE WITH THE HUB IS CONNECTED TO THE BLADES TO HOLD EACH BLADE IN PREDETERMINED POSITION WITH RESPECT TO ITS LONGITUDINAL AXIS AS THE BLADES ARE ROTATED. THE BLADE PITCH CONTROL MEANS IS LONGITUDINALLY SPACED FROM THE HUB AND MOUNTED FOR RECIPROCABLE MOVEMENT IN A PLANE PARALLEL TO THE LONGITUDINAL AXIS OF THE HUB. THE BLADE PITCH CONTROL MEANS INCLUDES A LINKAGE CONNECTED TO EACH BLADE AT A POINT SPACED FROM THE BLADE''S BALL JOINT CONNECTION TO THE HUB AND SPACED FROM THE LONGITUDINAL AXIS OF THE BLADE.

Method and apparatus for operating a propeller and driving engine fuel valve

Abstract: A control system for a variable pitch propeller having a driving engine with a fuel throttle in which the pitch of the propeller is automatically controlled to maintain substantially constant engine speed while the throttle is manually adjusted during takeoff and cruising, and the throttle is automatically adjusted to maintain substantially constant engine speed while the pitch of the propeller is manually adjusted during landing and taxiing. A single control lever is provided for selectively making one or the other system of operation effective.

Engine, propeller and rotor installations

Abstract: An engine propeller and rotor installation includes an enginedriven variable pitch propeller and a rotor which can, under certain conditions, be driven by the engines with the propeller. Propeller pitch is adjustable by a pitch control system in response to input or datum signals and in response to engine torque signals. These signals are applied to the system in a manner such that, without substantially reducing the power transmitted to the rotor, propeller blade pitch is changed to reduce power absorption by the propeller by an amount necessary for the engine to avoid reaching a stalled condition.

Safety device for variable pitch propellers

Abstract: A SAFETY DEVICE FOR VARIABLE PITCH MARINE PROPELLERS COMPRISES, ACCORDING TO A PREFERRED EMBODIMENT OF THE INVENTION, A HUB, PROPELLER BLADES ROTATABLY MOUNTED IN THE HUB FOR ADJUSTMENT OF THEIR PITCH, AND A FLUID MOTOR LOCATED IN THE HUB TO EFFECT SUCH ADJUSTMENT. A SECOND FLUID MOTOR IS NORMALLY INOPERATIVE, BUT, UPON FAILURE OF THE FIRST MOTOR, OPERATES, INDEPENDENT OF THE FIRST MOTOR, TO CHANGE THE PROPELLER PITCH TO ONE PROVIDING FORWARD MOVEMENT OF THE SHIP, REGARDLESS OF THE PITCH THEN ETABLISHED BY THE MAIN PITCH-CONTROL SYSTEM.

Suppression of transmitted harmonic rotor loads by blade pitch control

Abstract: : A method is developed for computing the pitch angle inputs required to eliminate the transmission of harmonic vertical forces from a helicopter rotor to its driving shaft. The inertia and aerodynamic forces due to dynamic blade motions are taken into account in the computations. In finding the aerodynamic loads, a realistic model is used which represents the wake vorticity by a mesh of segmented vortex filaments. Results of computations for three flight conditions are presented for a rotor which is approximately the same as the UH-1A configuration except for assumed differences in pitch control.

Bulldozer blade mounting

Abstract: A bulldozer blade mounting for minimizing mechanical stresses during tilting of the blade and for maintaining generally constant blade pitch during raising and lowering of the blade, comprising three generally parallel members pivotally mounted between the blade and its supporting vehicle Two of the members are parallel push arms arranged in a generally horizontal plane relatively adjacent the base of the blade The third member is an extendible link arranged in a generally central location between the vehicle and an upper portion of the blade to provide triangular support for the blade and to permit pitching of the blade